A phone company charges $30 a month for unlimited talk, text, and 2GB of data, and $2 for every gigabyte of data above 2GB.
Write an expression for the monthly phone charge, P, in dollars, as a function of the number of gigabytes of data, d, used that month.
For $0 \le d \le 2$
$P(d) = 30$
For $d > 2$
$P(d) = 2d + 30$